geometry triangle

One side of a triangle is 18 cm. Inside the triangle, a segment is drawn parallel to the 18-cm side, forming a trapezoid whose area is 1/3 that of the original triangle. Find the length of this segment. Help would be appreciated thanks!

One side of a triangle is 18 cm. Inside the triangle, a segment is drawn parallel to the 18-cm side, forming a trapezoid whose area is 1/3 that of the original triangle. Find the length of this segment. Help would be appreciated thanks!

I did not try to do the problem but it seems there is not enought infromation. Are you sure that is what they say?